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uprobes/x86: Don't use arch_uprobe_abort_xol() in arch_uprobe_post_xol()

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014940bad8 "uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails"
changed arch_uprobe_post_xol() to use arch_uprobe_abort_xol() if ->post_xol
fails. This was correct and helped to avoid the additional complications,
we need to clear X86_EFLAGS_TF in this case.

However, now that we have uprobe_xol_ops->abort() hook it would be better
to avoid arch_uprobe_abort_xol() here. ->post_xol() should likely do what
->abort() does anyway, we should not do the same work twice. Currently only
handle_riprel_post_xol() can be called twice, this is unnecessary but safe.
Still this is not clean and can lead to the problems in future.

Change arch_uprobe_post_xol() to clear X86_EFLAGS_TF and restore ->ip by
hand and avoid arch_uprobe_abort_xol(). This temporary uglifies the usage
of autask.saved_tf, we will cleanup this later.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
This commit is contained in:
Oleg Nesterov 2014-04-21 18:28:02 +02:00
parent 588fbd613c
commit 6ded5f3848
1 changed files with 9 additions and 8 deletions
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17
arch/x86/kernel/uprobes.c
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@ -759,22 +759,24 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
struct uprobe_task *utask = current->utask;
WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
current->thread.trap_nr = utask->autask.saved_trap_nr;
if (auprobe->ops->post_xol) {
int err = auprobe->ops->post_xol(auprobe, regs);
if (err) {
arch_uprobe_abort_xol(auprobe, regs);
if (!utask->autask.saved_tf)
regs->flags &= ~X86_EFLAGS_TF;
/*
* Restart the probed insn. ->post_xol() must ensure
* this is really possible if it returns -ERESTART.
* Restore ->ip for restart or post mortem analysis.
* ->post_xol() must not return -ERESTART unless this
* is really possible.
*/
regs->ip = utask->vaddr;
if (err == -ERESTART)
return 0;
return err;
}
}
current->thread.trap_nr = utask->autask.saved_trap_nr;
/*
* arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
* so we can get an extra SIGTRAP if we do not clear TF. We need
@ -819,9 +821,8 @@ int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val,
/*
* This function gets called when XOL instruction either gets trapped or
* the thread has a fatal signal, or if arch_uprobe_post_xol() failed.
* Reset the instruction pointer to its probed address for the potential
* restart or for post mortem analysis.
* the thread has a fatal signal. Reset the instruction pointer to its
* probed address for the potential restart or for post mortem analysis.
*/
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{